Why does Windows keep going back to the app tiles view when I close a window?

I have had multiple Outlook messages open in different windows and multiple excel spreadsheets. When I try to go from one to the other it takes me back to the app tile view. If I close an email in a separate window it takes me back to the app tile view. It used to take me back to Outlook.

This just started happening today after an automatic update last nite.